Light-emitting device, lighting device, and electronic device

ABSTRACT

It is an object to provide a flexible light-emitting device with high reliability in a simple way. Further, it is an object to provide an electronic device or a lighting device each mounted with the light-emitting device. A light-emitting device with high reliability can be obtained with the use of a light-emitting device having the following structure: an element portion including a light-emitting element is interposed between a substrate having flexibility and a light-transmitting property with respect to visible light and a metal substrate; and insulating layers provided over and under the element portion are in contact with each other in the outer periphery of the element portion to seal the element portion. Further, by mounting an electronic device or a lighting device with a light-emitting device having such a structure, an electronic device or a lighting device with high reliability can be obtained.

This application is a divisional of copending application Ser. No.12/824,795 filed on Jun. 28, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light-emitting device including alight-emitting element utilizing electroluminescence (EL). Further, thepresent invention relates to a lighting device manufactured using thelight-emitting device, or to an electronic device in which a displayportion is mounted with the light-emitting device.

2. Description of the Related Art

In recent years, a light-emitting device to be mounted in a display of atelevision set, a mobile phone, a digital camera, or the like, or in alighting device has been required to be flat and thin. A light-emittingdevice utilizing a self-luminous light-emitting element has attractedattention as a light-emitting device for meeting this requirement. Oneof the self-light-emitting elements is a light-emitting elementutilizing electroluminescence, and this light-emitting element includesa light-emitting material interposed between a pair of electrodes andcan provide light-emission from the light-emitting material by voltageapplication. Such a self-light-emitting element has a feature in thatthe thickness can be reduced and that response speed is extremely high.

In the next phase of this field, focus is placed on commercialization ofa flexible light-emitting device having a curved surface, and a varietyof proposals have been made (for example, see Patent Document 1). Alight-emitting device using a flexible support substrate can be highlylightweight compared to the case of using a glass substrate or the likeas a support substrate.

However, in commercialization of such a flexible light-emitting device,the biggest problem is its lifetime. The reason of the problem is that,in a flexible light-emitting device, a plastic substrate has to be usedas a support substrate which needs to support a light-emitting elementand to protect an element against moisture, oxygen, and the like in theoutside thereof. The plastic substrate has high water permeability andlow heat resistance, though it has flexibility. Because of the low heatresistance of the plastic substrate, a protective film with high qualitywhich needs a high-temperature process cannot be formed, and moistureentering from the plastic substrate side has a great influence on thelifetime of the light-emitting element, furthermore, the light-emittingdevice.

In Non-Patent Document 1, for example, an example in which alight-emitting element is formed over a substrate includingpolyethersulfone (PES) as a base and is sealed with an aluminum film toform a flexible light-emitting device is introduced; however, itslifetime is about 230 hours and the light-emitting device is miles awayfrom commercialization. In Non-Patent Documents 2 and 3, an example of aflexible light-emitting device in which a light-emitting element isformed over a stainless steel substrate is introduced. In this example,moisture and the like are prevented from entering from the stainlesssteel substrate side; however, moisture cannot be prevented effectivelyfrom entering from the light-emitting element side. Therefore, it isattempted to improve the lifetime with the use of, over thelight-emitting element, a sealing film in which plural kinds ofmaterials are stacked.

Although a thin metal film such as an aluminum film or a stainless steelsubstrate has both flexibility and low water permeability, it does nottransmit visible light therethrough with a normal thickness. Thus, inthe light-emitting device, a thin metal film or a stainless steelsubstrate is used for only one of a pair of substrates which sandwich alight-emitting element.

CITATION LIST Patent Document

[Patent Document 1] Japanese Published Patent Application No.2003-204049

Non-Patent Document

[Non Patent Document 1] Gi Heon Kim et al., IDW'03, 2003, pp. 387-390

[Non Patent Document 2] Dong Un Jin et al., SID 06 DIGEST, 2006, pp.1855-1857

[Non Patent Document 3] Anna Chwang et al., SID 06 DIGEST, 2006, pp.1858-1861

SUMMARY OF THE INVENTION

In view of the foregoing problem, it is an object of an embodiment ofthe present invention to provide a flexible light-emitting device withhigh reliability in a simple way. Further, it is an object to provide anelectronic device or a lighting device each mounted with thelight-emitting device.

The above problem can be solved with a light-emitting device having thefollowing structure: an element portion including a light-emittingelement is interposed between a substrate having flexibility and alight-transmitting property with respect to visible light and a metalsubstrate; and insulating layers provided over and under the elementportion are in contact with each other in the outer periphery of theelement portion to seal the element portion.

That is, an embodiment of the present invention is a light-emittingdevice including a substrate having flexibility and a light-transmittingproperty with respect to visible light; a first insulating layerprovided over the substrate; an element portion which is provided overthe first insulating layer and is provided with at least alight-emitting element and a switching element for applying a potentialto the light-emitting element; a second insulating layer covering a sidesurface and a top surface of the element portion; and a metal substratewhich is provided over the second insulating layer to face thesubstrate. In the light-emitting device, at least parts of the firstinsulating layer and the second insulating layer are in contact witheach other in an outer periphery of the element portion.

An embodiment of the present invention is a light-emitting deviceincluding a substrate having flexibility and a light-transmittingproperty with respect to visible light; a first insulating layerprovided over the substrate; an element portion which is provided overthe first insulating layer and is provided with at least alight-emitting element and a switching element for applying a potentialto the light-emitting element; a second insulating layer covering a sidesurface and a top surface of the element portion; a resin film providedover the second insulating layer; and a metal substrate which isprovided over the resin film to face the substrate. In thelight-emitting device, at least parts of the first insulating layer andthe second insulating layer are in contact with each other in an outerperiphery of the element portion.

In the above-described structure, a surface of the substrate which isopposite to a surface facing the light-emitting element may be providedwith a third insulating layer.

An embodiment of the present invention is a light-emitting deviceincluding a substrate having flexibility and a light-transmittingproperty with respect to visible light; a first insulating layerprovided over the substrate; an element portion which is provided overthe first insulating layer and is provided with at least alight-emitting element and a switching element for applying a potentialto the light-emitting element; a second insulating layer covering a sidesurface and a top surface of the element portion; a sealing materialwhich is provided over the second insulating layer and is provided tosurround an outer periphery of the element portion; and a metalsubstrate which is provided to face the substrate. In the light-emittingdevice, at least parts of the first insulating layer and the secondinsulating layer are in contact with each other in a region which is inan outer periphery of the element portion and is surrounded by thesealing material.

An embodiment of the present invention is an electronic device or alighting device each mounted with a light-emitting device having theabove-described structure.

Note that in this specification, the category of the term“light-emitting element” includes elements whose luminance is controlledby current or voltage, and specifically includes organic EL elements,inorganic EL elements, and the like.

The light-emitting device disclosed in this specification may be eithera passive matrix light-emitting device or an active matrixlight-emitting device.

The category of the light-emitting device in this specification includesimage display devices, light emitting devices, and light sources (e.g.,lighting devices). In addition, the category of the light-emittingdevice includes all types of modules such as a module in which a panelis attached with a connector such as an FPC (flexible printed circuit),a TAB (tape automated bonding) tape or a TCP (tape carrier package); amodule in which a printed wiring board is provided on the tip of a TABtape or a TCP; and a module in which an IC (integrated circuit) isdirectly mounted on a light-emitting element by the COG (chip on glass)technique.

Note that the ordinal numbers such as “first” and “second” in thisspecification are used for convenience and do not denote the order ofsteps and the stacking order of layers. In addition, the ordinal numbersin this specification do not denote particular names which specify thepresent invention.

In accordance with an embodiment of the present invention, alight-emitting device which has high reliability and is thinned can beprovided. Further, in accordance with an embodiment of the presentinvention, a lighting device or an electronic device with highreliability can be provided with the use of a light-emitting device withhigh reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C each illustrate a light-emitting device of an embodimentof the present invention;

FIGS. 2A to 2D each illustrate a light-emitting device of an embodimentof the present invention;

FIGS. 3A to 3C illustrate a method for manufacturing a light-emittingdevice of an embodiment of the present invention;

FIGS. 4A to 4D illustrate the method for manufacturing thelight-emitting device of an embodiment of the present invention;

FIGS. 5A and 5B illustrate the method for manufacturing thelight-emitting device of an embodiment of the present invention;

FIGS. 6A to 6C each illustrate an example of a structure of alight-emitting element;

FIGS. 7A and 7B illustrate an example of a structure of a light-emittingdevice of an embodiment of the present invention; and

FIGS. 8A and 8B each illustrate an application example of alight-emitting device of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below withreference to drawings. However, the present invention can be carried outin many different modes, and it is easily understood by those skilled inthe art that modes and details of the present invention can be modifiedin various ways without departing from the purpose and the scope of thepresent invention. Therefore, the present invention is not construed asbeing limited to description of the embodiments.

Embodiment 1

In this embodiment, examples of a light-emitting device will bedescribed with reference to FIGS. 1A to 1C. FIGS. 1A to 1C eachillustrate a display portion of a light-emitting device of thisembodiment.

The light-emitting device of this embodiment which is illustrated inFIG. 1A includes an element portion 150 and a first insulating layer 104over a substrate 100. A top surface and a side surface of the elementportion 150 are covered with a second insulating layer 140. Further, atleast parts of the first insulating layer 104 and the second insulatinglayer 140 are in contact with each other in end portions of thelight-emitting device where the element portion 150 is not present, sothat the element portion 150 is sealed. Note that it is preferable thatthe first insulating layer 104 and the second insulating layer 140 be incontact with each other so as to surround the outer periphery of theelement portion 150, and it is still preferable that a region where thefirst insulating layer 104 and the second insulating layer 140 are incontact with each other goes around twice the outer periphery of theelement portion 150. Further, a metal substrate 144 is provided to facethe substrate 100, and a resin film 142 is provided between the metalsubstrate 144 and the second insulating layer 140.

As the substrate 100, a substrate having flexibility and alight-transmitting property with respect to visible light can be used,and for example, it is preferable to use a polyester resin such aspolyethylene terephthalate (PET) or polyethylene naphthalate (PEN), apolyacrylonitrile resin, a polyimide resin, a polymethyl methacrylateresin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, apolyamide resin, a cycloolefin resin, a polystyrene resin, a polyamideimide resin, a polyvinylchloride resin, or the like. Alternatively, asthe substrate 100, a structure body in which a fibrous body isimpregnated with an organic resin can be used. However, as the substrate100, any substrate having flexibility and a light-transmitting propertywith respect to visible light can be used without particular limitation.

The first insulating layer 104 is formed over the substrate 100. Thefirst insulating layer 104 serves as a protective layer, so thatmoisture and gas such as oxygen can be prevented from entering theelement portion 150. Further, a semiconductor element or a wiring can beprevented from being damaged (e.g., the semiconductor element or thewiring can be prevented from being cracked) in separating an elementportion including the semiconductor element and the like from asubstrate for element formation with the use of a separation layer in aprocess of manufacturing a light-emitting device. The first insulatinglayer 104 is formed using a material having a light-transmittingproperty and low water permeability. For example, a material containingnitrogen and silicon, such as silicon nitride, silicon nitride oxide, orsilicon oxynitride, can be preferably used. The first insulating layer104 may be formed as a single layer or a multilayer. The firstinsulating layer 104 is preferably formed to a thickness of 10 nm to1000 nm inclusive, and still preferably a thickness of 100 nm to 700 nminclusive.

The element portion 150 is formed over the first insulating layer 104.The element portion 150 includes at least a light-emitting element 138and a switching element for applying a potential to the light-emittingelement 138. For example, a transistor (e.g., a bipolar transistor or aMOS transistor), a diode (e.g., a PN diode, a PIN diode, a Schottkydiode, a metal-insulator-metal (MIM) diode, ametal-insulator-semiconductor (MIS) diode, or a diode-connectedtransistor), a thyristor, or the like can be used as the switchingelement. Alternatively, a logic circuit in which such elements arecombined can be used as the switching element. In this embodiment, athin film transistor 106 is used as the switching element. Further, alight-emitting device may be a driver integrated type light-emittingdevice, so that a driver circuit portion may be included in the elementportion 150. Note that a driver circuit can be formed outside thesubstrates which are sealed.

The light-emitting element 138 includes a first electrode 130 serving asa pixel electrode, partition walls 137 covering end portions of thefirst electrode, an EL layer 134, and a second electrode 136. One of thefirst electrode 130 and the second electrode 136 serves as an anode andthe other thereof serves as a cathode.

The EL layer 134 included in the light-emitting element includes atleast a light-emitting layer. Further, the EL layer 134 can have astacked-layer structure including any of functional layers such as ahole injection layer, a hole transport layer, an electron transportlayer, an electron injection layer, and the like, in addition to thelight-emitting layer. The EL layer 134 can be formed using either a lowmolecular material or a high molecular material. Note that the materialforming the EL layer 134 is not limited to a material containing only anorganic compound material, and may partially contain an inorganiccompound material.

The top surface and the side surface of the element portion 150including the light-emitting element 138 are covered with the secondinsulating layer 140. Further, at least the parts of the firstinsulating layer and the second insulating layer are in contact witheach other in the end portions of the light-emitting device where theelement portion 150 is not present, so that the element portion 150 issealed.

The second insulating layer 140 serves as a protective layer, so thatmoisture and gas such as oxygen can be prevented from entering theelement portion 150. The second insulating layer 140 is formed using amaterial having a light-transmitting property and low waterpermeability. For example, a material containing nitrogen and silicon,such as silicon nitride, silicon nitride oxide, or silicon oxynitride;aluminum oxide; or the like can be preferably used. The secondinsulating layer 140 may be formed as a single layer or a multilayer.The second insulating layer 140 is preferably formed to a thickness of10 nm to 1000 nm inclusive, and still preferably a thickness of 100 nmto 700 nm inclusive.

In FIG. 1A, the resin film 142 is formed over the second insulatinglayer 140. Examples of materials used for formation of the resin film142 include an organic compound such as acrylic resins, polyimideresins, melamine resins, polyester resins, polycarbonate resins, phenolresins, epoxy resins, polyacetal, polyether, polyurethane, polyamide(nylon), furan resins, or diallylphthalate resins; inorganic siloxanepolymers including a Si—O—Si bond among compounds including silicon,oxygen, and hydrogen, formed by using a siloxane-polymer-based materialtypified by silica glass as a starting material; or organic siloxanepolymers in which hydrogen bonded with silicon is substituted by anorganic group such as methyl or phenyl, typified by alkylsiloxanepolymers, alkylsilsesquioxane polymers, silsesquioxane hydride polymers,or alkylsilsesquioxane hydride polymers. Alternatively, as the resinfilm 142, a structure body in which a fibrous body is impregnated withan organic resin can be used.

The metal substrate 144 facing the substrate 100 is provided over theresin film 142. The metal substrate 144 employed has a thickness of 10μm to 200 μm inclusive so as to be flexible. A material of the metalsubstrate 144 is not limited to a particular material, but it ispreferable to use aluminum, copper, nickel, an alloy such as an aluminumalloy or stainless steel, or the like. Since the metal substrate 144does not have a light-transmitting property with respect to visiblelight with a thickness in the above range although it has sufficientlylow water permeability and sufficiently high flexibility, thelight-emitting device in this embodiment is a so-called bottom emissionlight-emitting device in which light emission is extracted through thesubstrate 100 provided with a thin film transistor layer.

Note that a drying agent may be provided between the resin film 142 andthe metal substrate 144. By enclosing the drying agent therebetween,deterioration of the light-emitting element due to moisture and the likecan be further prevented. As the drying agent, a substance which adsorbsmoisture by chemical adsorption, such as an oxide of an alkaline earthmetal such as calcium oxide or barium oxide can be used. Alternatively,a substance which adsorbs moisture by physical adsorption such aszeolite or silica gel may be used as well, as the drying agent.

The light-emitting device of this embodiment which is illustrated inFIGS. 1A to 1C can be curved. Therefore, the light-emitting device ofthis embodiment can be bonded to various base materials. When thelight-emitting device of this embodiment is attached to a base materialhaving a curved surface, an electronic device such as a display having acurved surface or a lighting device having a curved surface can berealized.

Further, in the light-emitting device of this embodiment, the topsurface and the side surface of the element portion 150 are covered withthe second insulating layer 140 formed using a film having low waterpermeability. In addition, in the light-emitting device of thisembodiment, the second insulating layer 140 is in contact with the firstinsulating layer 104 in the end portions of the element portion 150, sothat the element portion 150 is sealed. Thus, moisture and gas such asoxygen can be prevented from entering the element portion 150.Accordingly, a highly reliable light-emitting device in whichdeterioration due to moisture or gas is suppressed can be obtained.

FIG. 1B illustrates a light-emitting device of this embodiment whosestructure is different from the structure illustrated in FIG. 1A. Thelight-emitting device of this embodiment which is illustrated in FIG. 1Bhas a structure in which a third insulating layer 152 is providedoutside the substrate 100 (the side opposite to the light-emittingelement 138) in the light-emitting device illustrated in FIG. 1A.

In the light-emitting device illustrated in FIG. 1B, moisture and gassuch as oxygen can be prevented from entering from the substrate 100side more effectively with the third insulating layer 152. Further, asurface of the substrate 100 which is a soft substrate formed usingresin or the like can be prevented from being scratched and can beprotected against pressures applied thereto, for example.

The third insulating layer 152 is formed as a single layer or amultilayer using an inorganic compound by a sputtering method, a plasmaCVD method, an application method, a printing method, or the like afterthe attachment of the metal substrate 144. The third insulating layer152 is preferably formed using a film having a transmitting propertywith respect to visible light and a high degree of hardness. Forexample, a film containing nitrogen and silicon, such as a siliconnitride film or a silicon nitride oxide film, can be preferably used.The third insulating layer 152 is preferably formed to a thickness of 10nm to 1000 nm inclusive, and still preferably a thickness of 100 nm to700 nm inclusive. Note that by the formation of the third insulatinglayer 152 in succession to the attachment of the metal substrate 144,the light-emitting element is not exposed to the air; therefore, thelight-emitting element can be prevented from deteriorating.

FIG. 1C illustrates a light-emitting device of this embodiment whosestructure is different from the structures illustrated in FIG. 1A andFIG. 1B.

The light-emitting device of this embodiment which is illustrated inFIG. 1C is an example of bonding the metal substrate 144 with the use ofa sealing material 156 surrounding the outer periphery of the elementportion over the second insulating layer 140, instead of using the resinfilm 142 covering the element portion 150 in the light-emitting deviceillustrated in FIG. 1A. In FIG. 1C, the sealing material 156 can beformed using a thermal curable epoxy resin, a UV curable acrylic resin,thermoplastic nylon, polyester, or the like by a dispenser method, aprinting method, a thermo-compression bonding method, or the like. Notethat a drying agent may be provided in a region surrounded by thesealing material.

In the light-emitting device illustrated in FIG. 1C, a surface of themetal substrate 144 facing the element portion 150 is provided with aninsulating film 154. The insulating film 154 can be formed to have asingle-layer structure or a stacked-layer structure using an inorganicmaterial such as an oxide of silicon or a nitride of silicon; an organicmaterial such as polyimide, polyamide, benzocyclobutene, acrylic, orepoxy; a siloxane material; or the like, by a CVD method, a sputteringmethod, a SOG method, a droplet discharge method, a screen printingmethod, or the like.

The insulating film 154 can prevent moisture and gas such as oxygen fromentering the light-emitting device more effectively because the adhesionto the sealing material 156 is improved. Note that in the case where themetal substrate 144 is provided with the insulating film 154, theinsulating film 154 is preferably formed after a surface of the metalsubstrate 144 is subjected to the etching treatment.

Further, in FIG. 1C, two pairs of groove portions (a first grooveportion 160 a and a second groove portion 160 b) are provided in the endportions of the element portion 150. In each groove portion, the firstinsulating layer 104 and the second insulating layer 140 are in contactwith each other, so that the element portion 150 is sealed. Note that itis preferable that the first groove portion 160 a and the second grooveportion 160 b be each formed to surround the outer periphery of theelement portion 150. With the two pairs of groove portions provided inthe end portions of the element portion 150 as illustrated in FIG. 1C,stress which is to be applied to the element portion 150 when thelight-emitting device is bended can be relieved. Thus, a light-emittingdevice having high resistance to bending can be obtained.

Note that the structures illustrated in FIGS. 1A to 1C can be used incombination.

Further, in FIGS. 1A to 1C, a driver circuit portion may be included inthe element portion 150. Furthermore, in FIGS. 1A to 1C, only onelight-emitting element 138 is illustrated; however, in the case wherethe light-emitting device in this embodiment is used for displaying animage, a pixel portion including a plurality of the light-emittingelements 138 is formed. When a full-color image is displayed, it isnecessary to obtain light of at least three colors, i.e., red, green,and blue. As a method for obtaining light of at least three colors,there are a method in which a necessary portion of each EL layer 134 isformed using an appropriate material in accordance with the color oflight emission, a method in which each color is obtained by forming alllight-emitting elements for emitting light of white and transmitting thelight through a color filter layer, a method in which each color isobtained by forming all light-emitting elements for emitting light ofblue or other colors with a shorter wavelength than blue andtransmitting the light through a color conversion layer, and the like.

FIGS. 2A to 2D each illustrate an example of how a color filter layer ora color conversion layer is placed. In FIGS. 2A to 2D, reference numeral200 denotes a color filter layer (or a color conversion layer). Thecolor filter layer (or the color conversion layer) 200 is provided forthe light-emitting element 138 of each color. And the color filterlayers of adjacent colors may be overlapped at a portion other than anopen region (a portion where the first electrode, the EL layer, and thesecond electrode are directly overlapped) of the light-emitting element138. The color filter layer 200 may be formed in only a pixel portion250 or in a region including a driver circuit portion 252. Note that thedriver circuit portion 252 may be provided outside the light-emittingdevice.

FIG. 2A illustrates an example of forming the color filter layer 200over a first interlayer insulating film 206 after a wiring 204 of a thinfilm transistor is formed, and of forming a second interlayer insulatingfilm over the color filter layer 200.

The second interlayer insulating film can be formed to have asingle-layer structure or a stacked-layer structure using an organicinsulating material such as polyimide, polyamide, benzocyclobutene,acrylic, or epoxy, or an inorganic insulating material such as an oxideof silicon or a nitride of silicon, for example. For example, asillustrated in FIG. 2A, a planarization film 208 which planarizes a stepdue to a color filter is formed using an organic insulating material,and then, a barrier film 210 using an inorganic insulating material isstacked over the planarization film 208. Thus, the second interlayerinsulating film can be formed. With the barrier film 210, thelight-emitting element can be prevented from being affected by gasgenerated from the color filter layer (or the color conversion layer)200, which is preferable. Note that as the second interlayer insulatingfilm, a multilayer in which a number of organic insulating materials andinorganic insulating materials are alternately stacked may be used.

In FIG. 2A, after the second interlayer insulating film is formed, acontact hole is formed in the planarization film 208. In addition, anelectrode 212 connecting the first electrode 130 of the light-emittingelement and the wiring 204 is formed, and the first electrode 130 of thelight-emitting element is provided.

Although FIGS. 2A to 2D each illustrate only a color filter (or a colorconversion layer) of a single color, color filters (or color conversionlayers) of red, green, and blue are formed at appropriate positions withappropriate shapes in a light-emitting device. Any arrangement can beadopted for the arrangement pattern of the color filters (or the colorconversion layers), and stripe arrangement, diagonal mosaic arrangement,triangle mosaic arrangement, and the like may be used. In addition, inthe case of using a white-light-emitting element and a color filter,RGBW four pixel arrangement may be used. The RGBW four pixel arrangementis pixel arrangement which has a pixel provided with a color filtertransmitting light of red, a pixel provided with a color filtertransmitting light of blue, a pixel provided with a color filter layertransmitting light of green, and a pixel not provided with a colorfilter layer; this arrangement is effective in reducing powerconsumption and the like. Light emitted from the white-light-emittingelement includes, for example, light of red, light of green, and lightof blue, preferably, those according to the National TelevisionStandards Committee (NTSC).

The color filter can be formed by using a known material. In the case ofusing a photosensitive resin as the color filter, the color filter layermay be patterned by exposing the color filter itself to light and thendeveloping it, but it is preferred to perform patterning by dry etchingsince a minute pattern is necessary.

FIG. 2B illustrates an example of forming the color filter layer 200after the formation of a thin film transistor, and forming the firstinterlayer insulating film 206 over the color filter layer 200. In FIG.2B, after the first interlayer insulating film 206 is formed, a contacthole is formed in the first interlayer insulating film 206, and thewiring 204 is formed. Then, the first electrode 130 of thelight-emitting element which is connected to the wiring 204 is provided.

FIG. 2C illustrates an example of a structure in which a color filtersubstrate 214 provided with the color filter layer 200 is placed. In thecase where a surface of the color filter substrate 214, which is notprovided with the color filter layer 200, is attached to the substrate100 with an adhesive, the color filter substrate 214 may be providedwith a coat film 216 for preventing the color filter layer 200 frombeing scratched, for example. In addition, although not illustrated, asurface of the color filter substrate 214, which is provided with thecolor filter layer 200, may be attached to the substrate 100. Note thatthe color filter substrate 214 is a substrate obtained by forming thecolor filter layer 200 on any of various types of substrates havingflexibility and a transmitting property with respect to visible light,for example, a substrate formed using a material similar to that for thesubstrate 100.

FIG. 2D illustrates an example of a structure in which a color filtersubstrate 218 where the substrate 100 is provided with the color filterlayer 200 in advance is directly attached to a layer which is separatedfrom a formation substrate. The color filter substrate 218 including thesubstrate 100 provided with the color filter layer 200 is directlyattached to the layer including the first electrode, whereby the numberof components can be reduced and the manufacturing cost can be reduced.As the above, how the color filter layer (or the color conversion layer)is placed is briefly described. In addition to the above, a black matrixmay be provided between light-emitting elements, or other knownstructures may be employed.

Note that the structures in each of which a color filter layer isprovided in the structure of the light-emitting device in FIG. 1A areillustrated as examples with the use of FIGS. 2A to 2D. However, thesestructures are applicable to the light-emitting device illustrated inFIG. 1B or FIG. 1C in a similar manner.

Note that the structure described in this embodiment can be combinedwith any of the structures described in other embodiments asappropriate.

Embodiment 2

An example of a method for manufacturing a light-emitting device anembodiment of which is shown in Embodiment 1 is described with referenceto FIGS. 3A to 3C, FIGS. 4A to 4D, and FIGS. 5A and 5B. In thisembodiment, the case of manufacturing the structure of thelight-emitting device illustrated in FIG. 1A is described as an example.

First, a separation layer 302 is formed over a substrate 300 having aninsulating surface, which is a formation substrate, and subsequently,the first insulating layer 104 is formed. The separation layer 302 andthe first insulating layer 104 can be formed in succession. By formingsuccessively, the surface of the separation layer 302 is not exposed tothe air, so that impurities can be prevented from being contained in theseparation layer 302 and the first insulating layer 104.

As the substrate 300, which is a formation substrate, a glass substrate,a quartz substrate, a sapphire substrate, a ceramic substrate, a metalsubstrate having an insulating layer on a surface thereof, or the likecan be used. Alternatively, a plastic substrate having heat resistanceto the processing temperature of this embodiment may be used. In themanufacturing process of a semiconductor device, a formation substratecan be selected as appropriate in accordance with the process.

Note that in this process, the case where the separation layer 302 isprovided on an entire surface of the substrate 300 is described;however, after the separation layer 302 may be provided on the entiresurface of the substrate 300 if needed, the separation layer 302 may beremoved selectively, whereby the separation layer may be provided onlyon a desired region. In addition, although the separation layer 302 isformed to be in contact with the substrate 300 in FIGS. 3A to 3C, aninsulating layer such as a silicon oxide film, a silicon oxynitridefilm, a silicon nitride film, or a silicon nitride oxide film may beformed to be in contact with the substrate 300, if needed, and then theseparation layer 302 may be formed to be in contact with the insulatinglayer.

The separation layer 302 is formed to have a single-layer structure or astacked-layer structure including a layer formed using an element suchas tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium(Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium(Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), orsilicon (Si); or an alloy material or a compound material containing anyof the elements as its main component by a sputtering method, a plasmaCVD method, an application method, a printing method, or the like. Acrystalline structure of a layer containing silicon may be any one of anamorphous structure, a microcrystalline structure, and a polycrystallinestructure. Note that an application method includes a spin-coatingmethod, a dispensing method and the like in its category here.

In the case where the separation layer 302 has a single-layer structure,it is preferable to form a tungsten layer, a molybdenum layer, or alayer containing a mixture of tungsten and molybdenum. Alternatively, alayer containing an oxide or an oxynitride of tungsten, a layercontaining an oxide or an oxynitride of molybdenum, or a layercontaining an oxide or an oxynitride of a mixture of tungsten andmolybdenum is formed. Note that the mixture of tungsten and molybdenumcorresponds to an alloy of tungsten and molybdenum, for example.

In a case where the separation layer 302 has a stacked-layer structure,a tungsten layer, a molybdenum layer, or a layer containing a mixture oftungsten and molybdenum is preferably formed as a first layer. An oxideof tungsten, molybdenum, or a mixture of tungsten and molybdenum; anitride of tungsten, molybdenum, or a mixture of tungsten andmolybdenum; an oxynitride of tungsten, molybdenum, or a mixture oftungsten and molybdenum; or a nitride oxide of tungsten, molybdenum, ora mixture of tungsten and molybdenum is preferably formed as a secondlayer.

In the case where the stacked-layer structure of a layer containingtungsten and a layer containing an oxide of tungsten is formed as theseparation layer 302, the layer containing tungsten may be formed first,which is followed by the formation of an insulating layer formed usingan oxide over the layer containing tungsten so that a layer containingan oxide of tungsten is formed at the interface between the tungstenlayer and the insulating layer. Further, the surface of the layercontaining tungsten may be subjected to thermal oxidation treatment,oxygen plasma treatment, or treatment using a strong oxidizing solutionsuch as ozone water to form a layer containing an oxide of tungsten. Theplasma treatment and the thermal treatment may be performed in anatmosphere of oxygen, nitrogen, or dinitrogen monoxide alone, or a mixedgas of any of these gasses and another gas. The same can be applied tothe case of forming a layer containing a nitride, an oxynitride, or anitride oxide of tungsten. After a layer containing tungsten is formed,a silicon nitride layer, a silicon oxynitride layer, or a siliconnitride oxide layer may be formed thereover.

The first insulating layer 104 is preferably formed as a single layer ora multilayer of an insulating film containing nitrogen and silicon, suchas silicon nitride, silicon oxynitride, or silicon nitride oxide.Further, the first insulating layer 104 can be formed by a sputteringmethod, a plasma CVD method, an application method, a printing method,or the like. For example, the first insulating layer 104 is formed at atemperature of 250° C. to 400° C. by a plasma CVD method, whereby adense film having very low water permeability can be obtained. Note thatthe first insulating layer 104 is preferably formed to a thickness of 10nm to 1000 nm inclusive, and still preferably a thickness of 100 nm to700 nm inclusive. The first insulating layer 104 facilitates separationat the interface with the separation layer 302 in a subsequentseparation step. Further, the semiconductor element or the wiring can beprevented from being cracked or damaged in the subsequent separationstep. Further, the first insulating layer 104 serves as a protectivelayer of a light-emitting device to be manufactured.

Next, the thin film transistor 106 is formed over the first insulatinglayer 104 (FIG. 3A). The thin film transistor 106 includes asemiconductor layer 106 a having at least a source region, a drainregion, and a channel formation region; a gate insulating layer 106 b;and a gate electrode 106 c. Note that in order to stabilizecharacteristics of the thin film transistor, a base insulating film maybe formed between the first insulating layer 104 and the semiconductorlayer 106 a. The base insulating film can be formed as a single layer ora multilayer by using an inorganic insulating film of silicon oxide,silicon nitride, silicon oxynitride, silicon nitride oxide, or the like.

The semiconductor layer 106 a is a layer formed using anon-single-crystal semiconductor which has a thickness of 10 nm to 100nm inclusive, preferably, 20 nm to 70 nm inclusive. As thenon-single-crystal semiconductor layer, a crystalline semiconductorlayer, an amorphous semiconductor layer, a microcrystallinesemiconductor layer, and the like can be given. As the semiconductor,silicon, germanium, a silicon germanium compound, or the like can begiven. In particular, it is preferable to apply a crystallinesemiconductor which is formed by crystallization through laserirradiation, rapid thermal annealing (RTA), heat treatment using anannealing furnace, or a method in which any of these methods arecombined. In the heat treatment, a crystallization method using a metalelement such as nickel which can promote crystallization of a siliconsemiconductor can be used.

The gate insulating layer 106 b is formed using an inorganic insulatorsuch as silicon oxide or silicon oxynitride to a thickness of 5 nm to200 nm inclusive, preferably 10 nm to 100 nm inclusive.

The gate electrode 106 c can be formed using metal or a polycrystallinesemiconductor doped with an impurity which has one conductivity type. Ina case of using metal, tungsten (W), molybdenum (Mo), titanium (Ti),tantalum (Ta), aluminum (Al), or the like can be used. Moreover, metalnitride obtained by nitriding metal can be used. Alternatively, astructure in which a first layer formed using the metal nitride and asecond layer formed using the metal are stacked may be used. At thistime, by forming the first layer using metal nitride, the first layercan serve as a barrier metal. In other words, the metal of the secondlayer can be prevented from diffusing into the gate insulating layer orinto the semiconductor layer that is provided in a layer lower than thegate insulating layer. In the case of employing a stacked-layerstructure, the gate electrode may have a shape in which the edge of thefirst layer extends beyond the edge of the second layer.

For the thin film transistor 106 which is formed by combining thesemiconductor layer 106 a, the gate insulating layer 106 b, the gateelectrode 106 c, and the like, various structures such as a single drainstructure, an LDD (Lightly-Doped Drain) structure, and a gate-overlappeddrain structure can be applied. Moreover, a multi-gate structure whichis equivalent to a structure where transistors, to which gate voltagehaving the same potential is applied, are serially connected; adual-gate structure where the semiconductor layer is sandwiched by gateelectrodes; a bottom-gate structure; or the like can be used.

Further, a thin film transistor using metal oxide or an organicsemiconductor material for a semiconductor layer may be used as the thinfilm transistor 106. As typical examples of the metal oxide, zinc oxide,an oxide of zinc gallium indium, and the like can be given.

Next, the wiring 204 which is electrically connected to the sourceregion and the drain region of the thin film transistor 106 is formed,and the first electrode 130 of the light-emitting element which iselectrically connected to the wiring 204 and serves as a pixel electrodeis formed. For example, a first interlayer insulating film is formed asa single layer or a multilayer to cover the thin film transistor 106,and the wiring 204 which may serve as either the source electrode or thedrain electrode is formed over the first interlayer insulating film. InFIG. 3A, the first interlayer insulating film 206 including two layers,insulating layers 206 a and 206 b, is formed. Then, the first electrode130 which is connected to the wiring 204 is formed. Note that a secondinterlayer insulating film may be formed over the wiring 204, and thefirst electrode may be formed over the second interlayer insulatingfilm.

The first interlayer insulating film 206 can be formed to have asingle-layer structure or a stacked-layer structure using an inorganicmaterial such as an oxide of silicon or a nitride of silicon; an organicmaterial such as polyimide, polyamide, benzocyclobutene, acrylic, orepoxy; a siloxane material; or the like, by a CVD method, a sputteringmethod, a SOG method, a droplet discharge method, a screen printingmethod, or the like. For example, a silicon nitride oxide film may beformed as the first insulating layer 206 a, and a silicon oxynitridefilm may be formed as the second insulating layer 206 b.

The wiring 204 preferably includes a combination of a low resistantmaterial like aluminum (Al) and a barrier metal using a metal materialhaving a high melting point such as titanium or molybdenum, for examplea stacked-layer structure of titanium (Ti) and aluminum (Al), molybdenum(Mo) and aluminum (Al), or the like.

The first electrode 130 is an electrode that is used as an anode or acathode of the light-emitting element. In the case of being used as theanode, a material with a high work function is preferably used. Forexample, a single-layer film such as an indium tin oxide film, an indiumtin oxide film containing silicon, a light-transmitting conductive filmformed by a sputtering method using a target in which indium oxide ismixed with zinc oxide (ZnO) of 2 to 20 wt %, a zinc oxide (ZnO) film, aconductive oxynitride film containing zinc and aluminum, a titaniumnitride film, a chromium film, a tungsten film, a Zn film, or a Pt film;a stacked-layer structure of a titanium nitride film and a filmcontaining aluminum as its main component; a three-layer structure of atitanium nitride film, a film containing aluminum as its main component,and another titanium nitride film; or the like can be used. When theanode has a stacked-layer structure, the anode can have low resistanceas a wiring and form a favorable ohmic contact.

In the case of being used as the cathode, a material with a low workfunction (Al, Ag, Li, Ca, or an alloy thereof such as MgAg, MgIn, AlLi,CaF₂, or calcium nitride) is preferably used. In the case where anelectrode used as the cathode is made to transmit light, a stack of athin metal film with a small thickness and a light-transmittingconductive film (an indium tin oxide film, an indium tin oxide filmcontaining silicon, a light-transmitting conductive film formed by asputtering method using a target in which indium oxide is mixed withzinc oxide (ZnO) of 2 to 20 wt %, a zinc oxide (ZnO) film, or the like)is preferably used as the electrode.

Next, the partition walls 137 are formed using an organic material or aninorganic material to cover the end portions of the first electrode 130(FIG. 3B). For example, the partition walls 137 can be formed usingpositive photosensitive polyimide. The partition walls 137 are eachformed to have a curved surface with a curvature at an upper end portionor a lower end portion thereof to ensure a favorable coverage by thefilms which are formed over the partition walls 137 later. Either anegative type which becomes insoluble in an etchant by light irradiationor a positive type which becomes soluble in an etchant by lightirradiation can be used as the partition walls 137. Alternatively, thepartition walls 137 can be formed to have a single-layer structure or astacked-layer structure of an organic material such as epoxy, polyimide,polyamide, polyvinylphenol, or benzocyclobutene, or a siloxane materialsuch as a siloxane resin.

In addition, the partition walls 137 can be subjected to plasmatreatment to be oxidized or nitrided; accordingly, a surface of thepartition walls 137 can be modified and thus a dense film can beobtained. By modifying the surface of the partition walls 137, thestrength of the partition walls 137 can be improved, and physical damagesuch as crack generation at the time of forming an opening portion orthe like or film reduction at the time of etching can be reduced.

Through the above process, an element formation layer 304 which is to beseparated can be formed.

Next, the insulating layer provided in the end portions of the substrate300 is removed by etching or the like to form a groove portion 160 so asto surround the outer periphery of the pixel portion 250 and the drivercircuit portion 252 (a region to be the element portion of thelight-emitting device) (FIG. 3C). In FIG. 3C, the partition walls 137,the first interlayer insulating film 206, and the gate insulating layer106 b are etched to expose the first insulating layer 104. Note that thegroove portion 160 may be formed to expose the film containing nitrogenand silicon. In the case where the first interlayer insulating film 206or the gate insulating layer 106 b is formed using the above materials,these films are not necessarily etched. Two or more groove portions 160which surround the outer periphery of the pixel portion 250 and thedriver circuit portion 252 may be formed.

Next, as illustrated in FIG. 4A, an adhesive sheet 305 is attached tothe element formation layer 304. For the adhesive sheet 305, a sheetwhich can be separated by light or heat is used. The adhesive sheet 305is attached, whereby stress that is applied to the element formationlayer 304 before and after separation can be reduced and damage to thethin film transistor 106 can be suppressed, as well as separation can beeasily performed.

Next, the element formation layer 304 including the thin film transistor106 and the like is separated from the substrate 300 (FIG. 4B). As aseparation method, any of various methods can be employed. For example,when a metal oxide layer is formed as the separation layer 302 on theside that is in contact with the first insulating layer 104, the metaloxide layer is weakened by crystallization so that the element formationlayer 304 can be separated from the substrate 300. In addition, when alight-transmitting substrate is used as the substrate 300 and a filmcontaining nitrogen, oxygen, hydrogen, or the like (e.g., an amorphoussilicon film containing hydrogen, an alloy containing hydrogen, an alloycontaining oxygen, or the like) is used as the separation layer 302, theseparation layer 302 is irradiated with laser beam through the substrate300, and nitrogen, oxygen, or hydrogen contained in the separation layeris evaporated so that the element formation layer 304 can be separatedfrom the substrate 300. Alternatively, the separation layer 302 may beetched to be removed such that the element formation layer 304 can beseparated from the substrate 300.

Alternatively, a method of removing the substrate 300 by mechanicalgrinding or a method of removing the substrate 300 by etching using ahalogen fluoride gas such as NF₃, BrF₃, ClF₃ or the like or HF, or thelike can be employed. In this case, the separation layer 302 is notnecessarily used. Further, separation can be performed as follows: ametal oxide layer is formed as the separation layer 302 on the side incontact with the first insulating layer 104 and is weakened bycrystallization, and a portion of the separation layer 302 is removed bya solution or by etching using a halogen fluoride gas such as NF₃, BrF₃,or ClF₃; thus, separation can occur in the weakened metal oxide layer.

Alternatively, it is also possible that a groove to expose theseparation layer 302 is formed by laser irradiation, by etching using agas, a solution or the like, or with a sharp knife or a scalpel, so thatthe element formation layer 304 can be separated from the substrate 300,for example at the interface between the separation layer 302 and thefirst insulating layer 104 serving as a protective layer, since thegroove triggers the separation. For example, as a separation method,mechanical force (a separation process with a human hand or with agripper, a separation process by rotation of a roller, or the like) maybe used. Further, a liquid may be dropped into the groove to allow theliquid to be infiltrated into the interface between the separation layer302 and the first insulating layer 104, which may be followed by theseparation of the element formation layer 304 from the separation layer302. Alternatively, a method can be employed in which a fluoride gassuch as NF₃, BrF₃, or ClF₃ is introduced into the groove, and theseparation layer is removed by etching with the use of the fluoride gasso that the element formation layer 304 is separated from the substrate300 having an insulating surface. Further alternatively, the separationmay be performed while pouring a liquid such as water during theseparation.

As another separation method, if the separation layer 302 is formedusing tungsten, separation can be conducted while the separation layeris being etched by a mixed solution of ammonia water and hydrogenperoxide water.

Subsequently, the substrate 100 having flexibility and alight-transmitting property with respect to visible light is bonded tothe element formation layer 304 in which part of the separation layer302 or the first insulating layer 104 is exposed by the separation fromthe substrate 300, with the use of an adhesive (FIG. 4C).

As a material of the adhesive, various curable adhesives, e.g., a lightcurable adhesive such as a UV curable adhesive, a reactive curableadhesive, a thermal curable adhesive, and an anaerobic adhesive can beused. As the material of the adhesive, an epoxy resin, an acrylic resin,a silicone resin, a phenol resin, or the like can be used. Note that astructure body in which a fibrous body is impregnated with an organicresin (so-called prepreg) can be used as the substrate 100. In the caseof using a prepreg as the substrate 100, the element formation layer 304and the substrate 100 can be fixed to each other by applying pressurewithout using an adhesive. At this time, as the organic resin for thestructure body, a reactive curable resin, a thermal curable resin, a UVcurable resin, or the like which is better cured by additional treatmentis preferably used.

Over the substrate 100, the protective film with low water permeability,such as a film containing nitrogen and silicon, e.g., silicon nitride orsilicon oxynitride, or a film containing nitrogen and aluminum such asaluminum nitride, may be formed in advance.

After the substrate 100 is provided, the adhesive sheet 305 is removedto expose the first electrode 130 (FIG. 4D).

Through the above, the element formation layer 304 in which the thinfilm transistor and up to the first electrode 130 of the light-emittingelement are formed can be manufactured over the substrate 100.

Next, the EL layer 134 is formed over the first electrode 130. The ELlayer 134 can be formed using either a low molecular material or a highmolecular material. Note that, a material forming the EL layer 134 isnot limited to a material containing only an organic compound material,and it may partly contain an inorganic compound material. Alternatively,the EL layer 134 may have at least a light-emitting layer, and asingle-layer structure that is formed using a single light-emittinglayer or a stacked-layer structure including layers having differentfunctions may be used. For example, functional layers such as a holeinjection layer, a hole transport layer, a carrier-blocking layer, anelectron transport layer, an electron injection layer, and the like canbe combined as appropriate in addition to a light-emitting layer. Notethat a layer having two or more functions of the functions of therespective layers may be included.

In addition, the EL layer 134 can be formed by either a wet process or adry process, such as an evaporation method; an inkjet method, aspin-coating method, a dip coating method, or a nozzle printing method.

Next, the second electrode 136 is formed over the EL layer 134. Thus,the light-emitting element 138 in which the first electrode 130, the ELlayer 134, and the second electrode 136 are stacked is manufactured. Inthis manner, the element portion 150 including the thin film transistor106 and the light-emitting element 138 can be formed. Note that one ofthe first electrode 130 and the second electrode 136 is used as ananode, and the other is used as a cathode.

In the case of being used as the anode, a material with a high workfunction is preferably used. For example, a single-layer film such as anindium tin oxide film, an indium tin oxide film containing silicon, alight-transmitting conductive film formed by a sputtering method using atarget in which indium oxide is mixed with zinc oxide (ZnO) of 2 to 20wt %, zinc oxide (ZnO), a conductive oxynitride film containing zinc andaluminum, a titanium nitride film, a chromium film, a tungsten film, aZn film, or a Pt film; a stacked-layer structure of titanium nitride anda film containing aluminum as its main component; a three-layerstructure of a titanium nitride film, a film containing aluminum as itsmain component, and another titanium nitride film; or the like can beused.

In the case of being used as the cathode, a material with a low workfunction (Al, Ag, Li, Ca, or an alloy thereof such as MgAg, MgIn, AlLi,CaF₂, or calcium nitride) is preferably used. In the case where anelectrode used as the cathode is made to transmit light, a stack of athin metal film with a small thickness and a light-transmittingconductive film (an indium tin oxide film, an indium tin oxide filmcontaining silicon, a light-transmitting conductive film formed by asputtering method using a target in which indium oxide is mixed withzinc oxide (ZnO) of 2 to 20 wt %, a zinc oxide (ZnO) film, or the like)is preferably used as the electrode.

In this embodiment, the first electrode 130 is used as the anode, andthe EL layer 134 has a structure in which a hole injection layer, a holetransport layer, a light-emitting layer, and an electron injection layerare sequentially stacked in that order over the first electrode 130.Various kinds of materials can be used for the light-emitting layer. Forexample, a fluorescent compound which exhibits fluorescence or aphosphorescent compound which exhibits phosphorescence can be used.

Next, the second insulating layer 140 is formed over the secondelectrode 136 so as to cover the top surface and the side surface of theelement portion 150 (FIG. 5A). The second insulating layer 140 serves asa protective layer to prevent moisture from entering the EL layer 134and prevent damage to the EL layer 134. The second insulating layer 140is formed also in the groove portion 160, whereby the first insulatinglayer 104 which is exposed in the groove portion 160 and the secondinsulating layer 140 come in contact with each other. The firstinsulating layer 104 and the second insulating layer 140 can be firmlybonded to each other in the groove portion because the first insulatinglayer 104 and the second insulating layer 140 are each formed using afilm containing nitrogen and silicon. Therefore, by the formation of thegroove portion surrounding the outer periphery of the element portion150, the element portion can be firmly sealed.

For example, the second insulating layer 140 is formed as a single layeror a multilayer using, for example, a material containing nitrogen andsilicon such as silicon nitride, silicon nitride oxide, or siliconoxynitride; aluminum oxide; or the like by a sputtering method, a plasmaCVD method, an application method, a printing method, or the like.Alternatively, the above-described inorganic insulating film and anorganic insulating film such as a resin film may be stacked, so that thesecond insulating layer 140 may be formed. With the second insulatinglayer, moisture and gas such as oxygen can be prevented from enteringthe element portion. The second insulating layer 140 serving as aprotective layer preferably has a thickness of 10 nm to 1000 nminclusive, and still preferably 100 nm to 700 nm inclusive.

Subsequently, the resin film 142 is formed over the second insulatinglayer 140. The resin film 142 can be formed, for example, in such amanner that a composition is applied by an application method and thendried by heating. The resin film 142 is preferably formed using amaterial with good adhesion to the second insulating layer 140. Inparticular, in the case where the resin film 142 is formed by anapplication method, examples of materials used for formation of theresin film 142 include an organic compound such as acrylic resins,polyimide resins, melamine resins, polyester resins, polycarbonateresins, phenol resins, epoxy resins, polyacetal, polyether,polyurethane, polyamide (nylon), furan resins, or diallylphthalateresins; inorganic siloxane polymers including a Si—O—Si bond amongcompounds including silicon, oxygen, and hydrogen, formed by using asiloxane-polymer-based material typified by silica glass as a startingmaterial; or organic siloxane polymers in which hydrogen bonded withsilicon is substituted by an organic group such as methyl or phenyl,typified by alkylsiloxane polymers, alkylsilsesquioxane polymers,silsesquioxane hydride polymers, or alkylsilsesquioxane hydridepolymers. Alternatively, as the resin film 142, a structure body inwhich a fibrous body is impregnated with an organic resin can be used.

Then, the metal substrate 144 is bonded onto the resin film 142 (FIG.5B). The metal substrate 144 may be bonded thereto using theabove-described adhesive, or the resin film 142 may be used instead ofthe adhesive. A material for forming the metal substrate is not limitedto a particular material, but it is preferable to use aluminum, copper,nickel, an alloy of metal such as an aluminum alloy or stainless steel,or the like. Note that the metal substrate 144 is preferably subjectedto baking in vacuum or plasma treatment in order that moisture attachedto the surface of the metal substrate 144 can be removed, before themetal substrate 144 is bonded.

The metal substrate 144 can also be bonded using a laminator. Forexample, there are a method in which a sheet-like adhesive is attachedto the metal substrate using a laminator and the metal substrate withthe sheet-like adhesive is further bonded to the light-emitting elementusing a laminator, a method in which an adhesive is printed on the metalsubstrate by screen printing or the like and the metal substrate withthe adhesive is bonded to the light-emitting element using a laminator,and the like. These processes are preferably performed under reducedpressure in order to reduce bubbles between the light-emitting elementand the metal substrate.

Through the above-described process, the light-emitting device which isan embodiment of the present invention can be manufactured.

This embodiment describes a method in which up to the first electrode130 of the light-emitting element of the light-emitting device providedwith the thin film transistor is formed over the formation substrate,which is followed by the separation. However, the invention disclosed inthis specification is not limited thereto. The separation and transfermay be performed after the light-emitting element 138 is formed (i.e.,after the second electrode 136 of the light-emitting element is formed).Alternatively, after only the first insulating layer 104 may be formedover the formation substrate, and separated and transferred to thesubstrate 100, a thin film transistor or a light-emitting element may bemanufactured. Further, in the case where a thin film transistor is notprovided, the first electrode 130 of the light-emitting element isformed first over the first insulating layer 104, whereby alight-emitting device can be manufactured in a similar manner.Furthermore, the resin film may be provided over a surface of the metalsubstrate 144 to protect the metal substrate.

Further, a fibrous body may be included in materials of the substrate100 and the resin film 142. The fibrous body is a high-strength fiber ofan organic compound or an inorganic compound. A high-strength fiber isspecifically a fiber with a high modulus of elasticity in tension or afiber with a high Young's modulus. As a typical example of ahigh-strength fiber, a polyvinyl alcohol based fiber, a polyester basedfiber, a polyamide based fiber, a polyethylene based fiber, an aramidbased fiber, a polyparaphenylene benzobisoxazole fiber, a glass fiber,or a carbon fiber can be given. As a glass fiber, there is a glass fiberusing E glass, S glass, D glass, Q glass, or the like. These fibers maybe used in a state of a woven fabric or a nonwoven fabric, andimpregnated with an organic resin, and the organic resin is cured toobtain a structure body. This structure body may be used as thesubstrate 100. When the structure body including the fibrous body andthe organic resin is used as the substrate 100, reliability againstbending or damaging due to local pressure can be increased, which ispreferable.

In the case where the substrate 100 includes the above-mentioned fibrousbody, in order to reduce prevention of light emitted from thelight-emitting element to the outside, the fibrous body is preferably ananofiber with a diameter of less than or equal to 100 nm. Further,refractive indexes of the fibrous body and the organic resin or theadhesive preferably match with each other.

In the light-emitting device of this embodiment, a metal substrate withlow water permeability is used as a support of the light-emittingdevice, so that moisture can be prevented from entering thelight-emitting element 138. Thus, a light-emitting device with longlifetime can be realized. Further, the first insulating layer 104 andthe second insulating layer 140 which serve as protective layers are incontact with each other in the end portions of the element portion 150,so that moisture and gas such as oxygen can be prevented from enteringthe light-emitting element 138. Thus, a highly reliable light-emittingdevice can be realized.

Further, in the light-emitting device of this embodiment, a thin filmtransistor can be manufactured over a formation substrate with high heatresistance. Therefore, it is possible to use a thin film transistorusing a crystalline semiconductor layer of crystalline silicon or thelike with high mobility. Thus, a pixel portion and a driver circuitportion using such a thin film transistor can be formed over onesubstrate, and accordingly, a light-emitting device can be manufacturedat low cost.

Note that the structure described in this embodiment can be combinedwith any of the structures described in other embodiments asappropriate.

Embodiment 3

In this embodiment, a structure of a light-emitting element included ina light-emitting device is specifically described with reference toFIGS. 6A to 6C.

FIG. 6A illustrates an example of the structure of a light-emittingelement. In the light-emitting element of FIG. 6A, the EL layer 134 isprovided between the first electrode 130 and the second electrode 136.Note that there is no particular limitation on a stacked-layer structureof the EL layer 134 as long as a light-emitting layer is included. TheEL layer 134 may be need in an appropriate combination of alight-emitting layer with a layer containing a substance having a highelectron transport property, a layer containing a substance having ahigh hole transport property, a layer containing a substance having ahigh electron injection property, a layer containing a substance havinga high hole injection property, a layer containing a bipolar substance(a substance having high electron transport and hole transportproperties), or the like. For example, the EL layer 134 can be formed inan appropriate combination of a hole injection layer, a hole transportlayer, a light-emitting layer, an electron transport layer, an electroninjection layer, and the like. In this embodiment, a structure isdescribed in which the EL layer 134 includes a hole injection layer, ahole transport layer, a light-emitting layer, and an electron transportlayer. Specific materials for forming each of the layers will be givenbelow.

The hole injection layer is a layer that is provided in contact with ananode and contains a substance with a high hole injection property. As asubstance with a high hole injection property, molybdenum oxide,vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or thelike can be used. In addition, the hole injection layer can also beformed using a phthalocyanine compound such as phthalocyanine(abbreviation: H₂Pc) or copper phthalocyanine (CuPC); an aromatic aminecompound such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) orN,N-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: DNTPD); a high molecule such aspoly(ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS); orthe like.

Alternatively, as the hole injection layer, a composite material of asubstance with a high hole transport property containing an acceptorsubstance can be used. It is to be noted that, by using such a substancewith a high hole transport property containing an acceptor substance, amaterial used to form an electrode may be selected regardless of itswork function. In other words, besides a material with a high workfunction, a material with a low work function can also be used as thefirst electrode 130. As the acceptor substance,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like can be given. In addition, atransition metal oxide can be given. In addition, an oxide of metalsthat belong to Group 4 to Group 8 of the periodic table can be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, and rheniumoxide are preferable since their electron-accepting property is high.Among these, molybdenum oxide is especially preferable since it isstable in the air and its hygroscopic property is low and is easilytreated.

As the substance having a high hole transport property used for thecomposite material, any of a variety of compounds such as an aromaticamine compound, a carbazole derivative, aromatic hydrocarbon, or a highmolecular compound (e.g., an oligomer, a dendrimer, or a polymer) can beused. The organic compound used for the composite material is preferablyan organic compound having a high hole transport property. Specifically,a substance having a hole mobility of 10⁻⁶ cm²/Vs or higher ispreferably used. However, other substances than the above-describedmaterials may also be used as long as the substances have higher holetransport properties than electron transport properties. The organiccompounds which can be used for the composite material will bespecifically shown below.

As aromatic amine compounds, for example, there areN,N-di(p-tolyl)-N,N-diphenyl-p-phenylenediamine (abbreviation: DTDPPA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N,N′-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B), and the like.

As carbazole derivatives which can be used for the composite material,the following can be given specifically:3-[4N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2);3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1); and the like.

In addition, examples of the carbazole derivatives which can be used forthe composite material include 4,4′-di(N-carbazolyl)biphenyl(abbreviation: CBP), 1,3,5-tris[4-(N-carbazoly)phenyl]benzene(abbreviation: TCPB), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: CzPA),1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and thelike.

Examples of the aromatic hydrocarbon which can be used for the compositematerial include 2-tert-butyl-9,10-di(2-naphthyl)anthracene(abbreviation: t-BuDNA); 2-tert-butyl-9,10-di(1-naphthyl)anthracene;9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA);2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA);9,10-di(2-naphthyl)anthracene (abbreviation: DNA);9,10-diphenylanthracene (abbreviation: DPAnth); 2-tert-butylanthracene(abbreviation: t-BuAnth); 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA);2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene;9,10-bis[2-(1-naphthyl)phenyl]anthracene;2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene;2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene; 9,9′-bianthryl;10,10′-diphenyl-9,9′-bianthryl;10,10′-bis(2-phenylphenyl)-9,9′-bianthryl;10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl; anthracene;tetracene; rubrene; perylene, and 2,5,8,11-tetra(tert-butyl)perylene.Besides those, pentacene, coronene, or the like can also be used. Asdescribed above, the aromatic hydrocarbon which has a hole mobility of1×10⁻⁶ cm²/Vs or higher and which has 14 to 42 carbon atoms isparticularly preferable.

The aromatic hydrocarbon which can be used for the composite materialmay have a vinyl skeleton. As the aromatic hydrocarbon having a vinylgroup, the following are given for example:4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi);9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA);and the like.

Examples of the substance used for the composite material furtherinclude high molecular compounds such as poly(N-vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA); andpoly[N,N-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD).

The hole transport layer is a layer which contains a substance with ahigh hole transport property. Examples of the substance having a highhole transport property include aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino] biphenyl (abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), and the like. The substances mentioned here aremainly ones which have a hole mobility of 10⁻⁶ cm²/Vs or higher.However, other substances than the above described materials may also beused as long as the substances have higher hole transport propertiesthan electron transport properties. The layer containing a substancewith a high hole transport property is not limited to a single layer,and two or more layers containing the aforementioned substances may bestacked.

Further, a high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK) or poly(-vinyltriphenylamine) (abbreviation: PVTPA)can also be used for the hole transport layer.

The light-emitting layer is a layer containing a light-emittingsubstance. The light-emitting layer may be either a so-calledlight-emitting layer of a single film including an emission centermaterial as its main component or a so-called light-emitting layer of ahost-guest type in which an emission center material is dispersed in ahost material.

There is no particular limitation on the light-emitting center substancethat is used, and known fluorescent materials or phosphorescentmaterials can be used. As fluorescent materials, for example, there areN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA), or another material with an emission wavelengthof 450 nm or greater, such as4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetramine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM), or2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM). As phosphorescent materials, for example, inaddition tobis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate(abbreviation: FIr6), there are phosphorescent materials with anemission wavelength in the range of 470 nm to 500 nm, such asbis[2-(4′,6′-difluorophenyppyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: FIrpic),bis[2-(3′,5′-bistrifluoromethylphenyl)pyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: Ir(CF₃ppy)₂(pic)), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate(abbreviation: FIracac); phosphorescent materials with an emissionwavelength of greater than or equal to 500 nm (materials which emitgreen light), such as tris(2-phenylpyridinato)iridium(III)(abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato)iridium(III)acetylacetonate (abbreviation:Ir(ppy)₂(acac)), tris(acetylacetonato)(monophenanthroline)terbium(III)(abbreviation: Tb(acac)₃(Phen)),bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation:Ir(bzq)₂(acac)),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(dpo)₂(acac)),bis[2-(4′-perfluorophenylphenyl)pyridinato]iridium(III)acetylacetonate(abbreviation: Ir(p-PF-ph)₂(acac)),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(bt)₂(acac)),bis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C^(3′)]iridium(III)acetylacetonate(abbreviation: Ir(btp)₂(acac)),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(piq)₂(acac)),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)),(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac)),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinatoplatinum(II)(abbreviation: PtOEP),tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: Eu(DBM)₃(Phen)), andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(Eu(TTA)₃(Phen)); and the like. The light-emitting center substances canbe selected from the above-mentioned materials or other known materialsin consideration of the emission color of each of the light-emittingelements.

When the host material is used, for example, the following can be given:metal complexes such as tris(8-quinolinolato)aluminum(III)(abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III)(abbreviation: Almq₃), bis(10-hydroxybenzo[h]quinolinato)beryllium(II)(abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), and9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11); and aromatic amine compounds such as NPB (or a-NPD), TPD, andBSPB. In addition, condensed polycyclic aromatic compounds such asanthracene derivatives, phenanthrene derivatives, pyrene derivatives,chrysene derivatives, and dibenzo[g,p]chrysene derivatives are given.Specific examples of the condensed polycyclic aromatic compound include9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzAlPA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″,-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: CzPA),3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),3,3′,3″-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3), and thelike. From these materials or other known materials, a material may beselected which has a larger energy gap (or a triplet energy if thematerial emits phosphorescence) than an emission center materialdispersed in the material and which has a transport property as needed.

The electron transport layer is a layer that contains a substance with ahigh electron transport property. For example, a layer containing ametal complex having a quinoline skeleton or a benzoquinoline skeleton,such as tris(8-quinolinolato)aluminum (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), or the like can be used. Alternatively, a metal complex having anoxazole-based or triazole-based ligand, such asbis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂), orthe like can be used. Besides the metal complexes,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or the like can also be used. Thesubstances mentioned here are mainly ones that have an electron mobilityof 10⁻⁶ cm²/Vs or higher. The electron transport layer may be formedusing other materials than those described above as long as thematerials have electron transport properties higher than hole transportproperties.

Furthermore, the electron transport layer is not limited to a singlelayer, and two or more layers made of the aforementioned substances maybe stacked.

Further, a layer for controlling transport of electron carriers may beprovided between the electron transport layer and the light-emittinglayer. Specifically, the layer for controlling transport of electroncarriers is a layer formed by adding a small amount of substance havinga high electron trapping property to the material having a high electrontransport property as described above, so that carrier balance can beadjusted by controlling a transport of the electron carriers. Such astructure is very effective in suppressing a problem (such as shorteningof element lifetime) caused when electrons pass through thelight-emitting layer.

Further, an electron injection layer may be provided so as to be incontact with the electrode functioning as a cathode. As the electroninjection layer, an alkali metal, an alkaline earth metal, or a compoundthereof such as lithium fluoride (LiF), cesium fluoride (CsF), orcalcium fluoride (CaF₂) may be used. For example, a layer of a materialhaving an electron transport property containing an alkali metal, analkaline earth metal, or a compound thereof, such as an Alq layer whichcontains magnesium (Mg), may be used. When a layer made of a substancehaving electron transport properties, in which an alkali metal or analkaline earth metal is included, is used as the electron injectionlayer, electrons are efficiently injected from the second electrode 136,which is preferable.

When the second electrode 136 of the light-emitting element is used as acathode, a metal, an alloy, an electrically conductive compound, amixture thereof, or the like having a low work function (specifically, awork function of 3.8 eV or lower), can be used as a substance for thesecond electrode 136. As a typical example of such a cathode material,an element belonging to Group 1 or Group 2 of the periodic table, i.e.,an alkali metal such as lithium (Li) or cesium (Cs), or an alkalineearth metal such as magnesium (Mg), calcium (Ca), or strontium (Sr); analloy containing any of these (such as MgAg or AlLi); a rare earth metalsuch as europium (Eu) or ytterbium (Yb); an alloy containing such a rareearth metal; or the like can be used. However, when the electroninjection layer is provided between the cathode and the electrontransport layer, any of a variety of conductive materials such as Al,Ag, ITO, indium oxide-tin oxide containing silicon or silicon oxide, andthe like can be used regardless of its work function as the cathode.These conductive materials can be formed by a sputtering method, aninkjet method, a spin-coating method, or the like.

It is preferable that, when the second electrode 136 is used as ananode, the second electrode 136 be formed using a metal, an alloy, aconductive compound, a mixture thereof, or the like having a high workfunction (specifically, a work function of 4.0 eV or higher). Inparticular, examples thereof include indium oxide-tin oxide (ITO: indiumtin oxide), indium oxide-tin oxide containing silicon or silicon oxide,indium oxide-zinc oxide (IZO: indium zinc oxide), indium oxidecontaining tungsten oxide and zinc oxide (IWZO), and the like. Films ofthese conductive metal oxides are usually formed by sputtering; however,a sol-gel method or the like may also be used. For example, indiumoxide-zinc oxide (IZO) can be formed by a sputtering method using indiumoxide into which zinc oxide of 1 to 20 wt % is added, as a target.Moreover, indium oxide (IWZO) including tungsten oxide and zinc oxidecan be formed by a sputtering method using a target in which 0.5 to 5 wt% of tungsten oxide and 0.1 to 1 wt % of zinc oxide with respect toindium oxide are included. In addition, gold (Au), platinum (Pt), nickel(Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt(Co), copper (Cu), palladium (Pd), a nitride of a metal material (suchas titanium nitride), or the like can be used. By forming theabove-mentioned composite material so as to be in contact with theanode, a material for the electrode can be selected regardless of itswork function.

Note that a plurality of the above-mentioned EL layers 134 may bestacked between the first electrode 130 and the second electrode 136 asillustrated in FIG. 6B. In this case, a charge generation layer 600 ispreferably provided between the EL layers 134 which are stacked. Thecharge generation layer 600 can be formed by using the above-mentionedcomposite material. Further, the charge generation layer 600 may have astacked-layer structure including a layer containing the compositematerial and a layer containing another material. In this case, as thelayer containing another material, a layer containing an electrondonating substance and a substance with a high electron transportproperty, a layer comprising a transparent conductive film, and the likecan be used. As for a light-emitting element having such a structure,problems such as energy transfer and quenching occur with difficulty,and a light-emitting element which has both high light emissionefficiency and long lifetime can be easily obtained due to expansion inthe choice of materials. Moreover, a light-emitting element whichprovides phosphorescence from one of the EL layers and fluorescence fromthe other of the EL layers can be readily obtained. Note that thisstructure can be combined with the above-mentioned structures of the ELlayer.

Next, the case where three or more EL layers are stacked between thefirst electrode and the second electrode will be described. Asillustrated in FIG. 6C, in the case where n (n is a natural number ofthree or more) EL layers 134 are stacked, the charge generation layer600 is provided between an m-th (m is a natural number, 1≦m≦n−1) ELlayer and an (m+1)-th EL layer.

Note that the charge generation layer 600 has a function of injectingholes to one EL layer 134 which is formed in contact with one surface ofthe charge generation layer 600 and a function of injecting electrons tothe other EL layer 134 which is formed in contact with the other surfaceof the charge generation layer 600, when voltage is applied to the firstelectrode 130 and the second electrode 136.

The charge generation layer 600 may be formed using a composite materialof an organic compound and a metal oxide, a metal oxide, or a compositematerial of an organic compound and an alkali metal, an alkaline earthmetal, or a compound thereof; alternatively, these materials may becombined as appropriate. The composite material of an organic compoundand a metal oxide includes, for example, an organic compound and a metaloxide such as V₂O₅, MoO₃, or WO₃. As the organic compound, variouscompounds such as an aromatic amine compound, a carbazole derivative,aromatic hydrocarbon, and a high molecular compound (oligomer,dendrimer, polymer, or the like) can be used. As the organic compound,it is preferable to use the organic compound which has a hole transportproperty and has a hole mobility of 10⁻⁶ cm²/Vs or higher. However,other substances than the above described materials may also be used aslong as the substances have higher hole transport properties thanelectron transport properties. These materials used for the chargegeneration layer 600 are excellent in carrier-injecting property andcarrier-transporting property, and thus, a light-emitting element can bedriven with low current and with low voltage.

As in the structure illustrated in FIG. 6B or FIG. 6C, by arranging aplurality of EL layers to be partitioned from each other with a chargegeneration layer between a pair of electrodes, light emission in a highluminance region can be achieved with current density kept low. Sincecurrent density can be kept low, a light-emitting element having longlifetime can be realized. Further, by forming EL layers to emit light ofdifferent colors from each other, a light-emitting element as a wholecan provide light emission of a desired color. For example, by forming alight-emitting element having two EL layers such that the emission colorof the first EL layer and the emission color of the second EL layer arecomplementary colors, the light-emitting element can provide white lightemission as a whole. Note that the word “complementary” means colorrelationship in which an achromatic color is obtained when colors aremixed. That is, when lights obtained from substances, which emitcomplementary colored light each other are mixed, white light emissioncan be obtained. Further, the same can be applied to a light-emittingelement having three EL layers. For example, the light-emitting elementas a whole can provide white light emission when the emission color ofthe first EL layer is red, the emission color of the second EL layer isgreen, and the emission color of the third EL layer is blue.

Note that the structure described in this embodiment can be combinedwith any of the structures described in other embodiments asappropriate.

Embodiment 4

In this embodiment, a modular light-emitting device to which an FPC isconnected will be described with reference to FIGS. 7A and 7B. FIG. 7Ais a top view illustrating the light-emitting device manufactured by themanufacturing method described in Embodiment 2 as an example. FIG. 7B isa cross-sectional view taken along a line A-A′ of FIG. 7A.

In FIG. 7A, a first insulating layer is provided over the substrate 100having flexibility and a light-transmitting property with respect tovisible light. In addition, a pixel portion 502, a source side drivercircuit 504, and a gate side driver circuit 503 are formed over thefirst insulating layer. The pixel portion and the driver circuits can beobtained in accordance with Embodiment 2. Reference numeral 144 denotesa metal substrate which is bonded onto the pixel portion and the drivercircuit portion.

Reference numeral 508 denotes a wiring for transmitting a signalinputted to the source side driver circuit 504 and the gate side drivercircuit 503, and the wiring 508 receives a video signal, a clock signal,a start signal, a reset signal, and the like from a flexible printedcircuit (FPC) 402 which is to be an external input terminal. The wiring508 can be formed in the same process as that of forming the gateelectrodes of the thin film transistors provided in the pixel portionand the driver circuit portion. Note that a structure in which a printedwiring board (PWB) is attached to the FPC 402 illustrated in FIGS. 7Aand 7B may be used. The light-emitting device in this specificationincludes, in its category, not only the light-emitting device itself butalso the light-emitting device provided with the FPC or the PWB.

Next, the cross-sectional structure is described with reference to FIG.7B. The first insulating layer 104 is provided over the substrate 100,and the pixel portion 502 and the gate side deriver circuit 503 areformed over the first insulating layer 104. The pixel portion 502includes a plurality of pixels each including a current control TFT 511and a first pixel electrode 512 electrically connected to a drain of thecurrent control TFT 511. Further, the gate side driver circuit 503 isformed using a CMOS circuit in which an n-channel TFT 513 and ap-channel TFT 514 are combined.

Note that the connection form of the FPC is not limited to the structureillustrated in FIGS. 7A and 7B. For example, a through wiring can beprovided in a portion to be connected to the wiring 508 from thesubstrate 100 side, and, with the use of the through wiring, theconnection to the FPC can be realized. For example, a through-hole whichreaches the wiring 508 is formed in the substrate 100 and the firstinsulating layer 104 with the use of a laser, a drill, a punchingneedle, or the like, and a conductive resin is provided in thethrough-hole by screen printing or an inkjet method, whereby the throughwiring can be formed. The conductive resin refers to a resin in which aconductive particle with a grain size of several tens of micrometers orless is dissolved or resolved in an organic resin.

For the conductive particle, a conductive paste containing any of metalelements of copper (Cu), silver (Ag), nickel (Ni), gold (Au), platinum(Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), or titanium (Ti)can be used, for example. In addition, as an organic resin contained inthe conductive resin, one or more of organic resins functioning as abinder, a solvent, a dispersing agent, and a coating material for themetal particle can be used. Typically, an organic resin such as an epoxyresin, a phenol resin, or a silicone resin can be used.

In the case where a structure body in which a fibrous body isimpregnated with an organic resin is used as the substrate 100, thethrough wiring can be formed in the following manner. A conductive resinis arranged onto a predetermined position of the structure body. Part ofthe organic resin in the structure body is melted due to a reactionbetween the organic resin in the structure body and the organic resinincluded in the conductive resin, so that the structure body ispenetrated with a metal particle included in the conductive resin. Insuch a manner, the through wiring can be formed.

In this manner, the modular light-emitting device to which the FPC 402is connected can be obtained.

Note that the structure described in this embodiment can be combinedwith any of the structures described in other embodiments asappropriate.

Embodiment 5

In this embodiment, an electronic device and a lighting device eachincluding the light-emitting device described in the above embodiment inpart thereof will be described.

As examples of the electronic device including any of the light-emittingdevices described in Embodiments 1 to 4, the following can be given:video cameras, digital cameras, goggle type displays, navigationsystems, audio replay devices (e.g., car audio systems and audiosystems), computers, game machines, portable information terminals(e.g., mobile computers, cellular phones, portable game machines, andelectronic book readers), image replay devices in which a recordingmedium is provided (specifically, devices that are capable of replayingrecording media such as digital versatile discs (DVDs) and equipped witha display device that can display an image), and the like.

For example, FIG. 8A illustrates a flexible display which includes amain body 9601, a display portion 9602, an insert portion of an externalmemory 9603, a speaker portion 9604, operation keys 9605, and the like.The main body 9601 may be provided with an antenna for receiving atelevision broadcast, an external input terminal, an external outputterminal, a battery, and the like. In this display, the display portion9602 is manufactured using any of the light-emitting devices describedin Embodiments 1 to 4. The flexible display portion 9602 can be rolledup and stored in the main body 9601 and is suitable for being carried.The display mounted with the light-emitting device which is flexible,has long lifetime, and can easily be manufactured allows the displayportion 9602 to be suitable for being carried along and be lightweight,and further, the display can be a relatively inexpensive product withlong lifetime.

The light-emitting device relating to an embodiment of the presentinvention can be a passive matrix light-emitting device, and thelight-emitting device can be used for a lighting device. For example,FIG. 8B is a desk lamp including a lighting portion 9501, a support9503, a support base 9505, and the like. The lighting portion 9501 isformed using any of the light-emitting devices described in the aboveembodiments. Because the lighting portion 9501 is formed using aflexible light-emitting device, the lighting device described in thisembodiment can be a lighting device having a curved surface or alighting device having a flexible lighting portion. The use of aflexible light-emitting device for a lighting device as above not onlyimproves the degree of freedom in design of the lighting device but alsoenables the lighting device to be mounted onto a portion having a curvedsurface, such as the ceiling of a car. Further, with the use of aflexible light-emitting device, a lighting device can be manufactured inwhich its lighting portion can be rolled up and stored when not in use,like for example, a roller screen type lighting device. Note that theterm “lighting device” also includes, in its category, ceiling lights(ceiling-fixed lighting devices), wall lights (wall-hanging lightingdevices), and the like.

Note that the lighting device of this embodiment which is manufacturedby using any of the above embodiments can be a highly reliable lightingdevice.

In the above-described manner, an electronic device or a lighting devicecan be obtained by using any of the light-emitting devices described inthe above embodiments. The application range of the light-emittingdevice is so wide that the light-emitting device can be applied toelectronic devices or lighting devices in all fields, without limitationto the structure illustrated in FIG. 8A or FIG. 8B.

Note that the structure described in this embodiment can be combinedwith any of the structures described in other embodiments asappropriate.

This application is based on Japanese Patent Application serial no.2009-157742 filed with Japan Patent Office on Jul. 2, in 2009, theentire contents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: a substratehaving flexibility and a light-transmitting property with respect tovisible light; a first insulating layer over the substrate; an elementportion over the first insulating layer, wherein the element portioncomprises a light-emitting element and a switching element for applyinga potential to the light-emitting element; a second insulating layercovering a side surface and a top surface of the element portion; asealing material over the second insulating layer, wherein the sealingmaterial surrounds an outer periphery of the element portion; and ametal substrate overlapping with the light-emitting element, wherein thefirst insulating layer and the second insulating layer are in directcontact with each other in a region which is in the outer periphery ofthe element portion and is surrounded by the sealing material, whereinthe switching element comprises a semiconductor layer, and wherein thesemiconductor layer is totally over the first insulating layer.
 2. Thelight-emitting device according to claim 1, wherein the substratecomprises a fibrous body impregnated with an organic resin.
 3. Thelight-emitting device according to claim 1, wherein the first insulatinglayer and the second insulating layer are in contact with each other tosurround the element portion.
 4. The light-emitting device according toclaim 1, wherein another resin film is provided over the metalsubstrate.
 5. The light-emitting device according to claim 1, whereinthe metal substrate comprises any one of stainless steel, aluminum,copper, nickel, and an aluminum alloy.
 6. The light-emitting deviceaccording to claim 1, wherein the metal substrate has a thickness of 10μm to 200 μm inclusive.
 7. An electronic device comprising thelight-emitting device according to claim 1 in a display portion.
 8. Alighting device comprising the light-emitting device according toclaim
 1. 9. The light-emitting device according to claim 1, wherein thefirst insulating layer comprises any one of silicon nitride, siliconoxynitride and silicon nitride oxide.
 10. The light-emitting deviceaccording to claim 1, wherein the second insulating layer comprises anyone of silicon nitride, silicon nitride oxide, silicon oxynitride andaluminum oxide.
 11. The light-emitting device according to claim 1,wherein the metal substrate has flexibility.
 12. The light-emittingdevice according to claim 1, wherein the metal substrate faces a wholearea of the element portion.
 13. The light-emitting device according toclaim 1, wherein the light-emitting element comprises EL layers whichare stacked with each other.
 14. A flexible display comprising thelight-emitting device according to claim 1 in a display portion.
 15. Alight-emitting device comprising: a first layer having flexibility and alight-transmitting property with respect to visible light, the firstlayer comprising an aramid; a first insulating layer over the firstlayer; an element portion over the first insulating layer, wherein theelement portion comprises a light-emitting element and a switchingelement for applying a potential to the light-emitting element; a secondinsulating layer covering a side surface and a top surface of theelement portion; a third insulating layer surrounding an outer peripheryof the light-emitting element; and a second layer facing the firstlayer, the second layer comprising an aramid, wherein the firstinsulating layer and the second insulating layer are in direct contactwith each other in a region which is in the outer periphery of thelight-emitting element and is surrounded by the third insulating layer,wherein the switching element comprises a semiconductor layer, andwherein the semiconductor layer is totally over the first insulatinglayer.
 16. The light-emitting device according to claim 15, wherein thefirst insulating layer and the second insulating layer are in contactwith each other to surround the light-emitting element.
 17. Thelight-emitting device according to claim 15, wherein a part of the thirdinsulating layer is located below the first layer.
 18. Thelight-emitting device according to claim 15, wherein a fourth insulatinglayer is provided between the first insulating layer and the secondinsulating layer, and a part of the second insulating layer is locatedin an opening of the fourth insulating layer.
 19. The light-emittingdevice according to claim 15, wherein the light-emitting elementcomprises EL layers which are stacked with each other.
 20. A flexibledisplay comprising the light-emitting device according to claim 15 in adisplay portion.
 21. A light-emitting device comprising: a first layercomprising an aramid; a first insulating layer over the first layer; asemiconductor layer totally over the first insulating layer; a firstelectrode over the first insulating layer; a second insulating layerover the first electrode; an electroluminescent layer over the firstelectrode and the second insulating layer; a second electrode over theelectroluminescent layer; a third insulating layer over the secondelectrode; a fourth insulating layer outside the first layer and facingto a side surface of the first insulating layer and a side surface ofthe third insulating layer; and a second layer facing the first layer,the second layer comprising an aramid, wherein the first insulatinglayer and the third insulating layer are in direct contact with eachother, and the third insulating layer is in contact with a side surfaceof the second insulating layer.
 22. The light-emitting device accordingto claim 21, wherein the first insulating layer and the third insulatinglayer are in contact with each other to surround the first electrode,the second insulating layer, the electroluminescent layer, and thesecond electrode.
 23. The light-emitting device according to claim 21,wherein a part of the fourth insulating layer is located below the firstlayer.
 24. The light-emitting device according to claim 21, wherein apart of the third insulating layer is located in an opening of thesecond insulating layer.
 25. The light-emitting device according toclaim 21, wherein a charge generation layer and anotherelectroluminescent layer are provided over the electroluminescent layer.26. A flexible display comprising the light-emitting device according toclaim 21 in a display portion.